In recent years there has been an increased demand placed on materials producers to develop corrosion resistant, stronger and lighter materials. In an effort to meet this demand, materials producers have turned towards the use of reinforced composite plastic materials, such as ceramic reinforced plastic composites. A typical ceramic reinforced composite plastic material comprises a plastic matrix (thermosplastic and/or thermosetting) having ceramic reinforcement material therein.
One particular type of composite material, glass fiber reinforced plastic composites, has received added attention in recent years due to its applications in industries such as automotive, aerospace, electronic, appliance, construction, and marine. For example, Sheet Molding Compound (SMC) has become a popular choice for these applications. Sheet molding compound is a composite material typically comprising a thermosetting resin, glass fiber reinforcement, inorganic fillers, and small amounts of catalysts and other additives. Because of the presence of a thermosetting matrix material, like many modern composite materials, sheet molding compound cannot readily be melted. Consequently, as with many thermosetting-plastic containing materials, sheet molding compound is generally regarded as non-recyclable.
At present, one of the most economical methods for disposal of reinforced plastic composites, including scrap and factory waste, is to bury such material in a landfill. Unfortunately, landfill sites are increasingly becoming more scarce. As a result, costs have increased to use presently available landfill sites. Thus, there has been an increased need felt to develop a process whereby scrap and waste reinforced plastic composites can be recycled and used in the manufacture of new articles.
Several methods for recycling reinforced thermosetting plastic composites have been proposed. One method is to collect the scrap, and then shred and grind it. This idea is disclosed in connection with recycling thermosetting materials in U.S. Pat. No. 3,995,819, issued Dec. 7, 1976. Depending on the final size of the shredded particles, the resulting shredded material is then used as a filler material, blended in various matrices as discussed in U.S. Pat. No. 4,344,579, issued Aug. 17, 1982; and U.S. Pat. No. 4,123,584, issued Oct. 31, 1978. Unfortunately, there are drawbacks to this method, including the fact that various matrices require different particle sizes. To produce such a variety of useful particle sizes it is necessary to use special equipment, which entails high operational and maintenance costs. Further, the performance characteristics of the ground material, as a filler in many materials, has not yet been demonstrated.
It has been suggested that sheet molding compound scrap could be incinerated to recover the fuel energy present in the organic portion (i.e. the thermosetting polymer portion) of the compound. Unfortunately, incineration results in high ash content (50% to 60%). This ash still requires disposal, thereby failing to significantly reduce the waste disposal problem previously discussed.
It is a present practice in the nuclear waste containment industry to encapsulate contaminated material in glass encasements. This is accomplished by fusing a mass of sand around the contaminated material to form a glass charge. The charge, however, has no further recyclable uses and must be buried.